In a vehicle, a hydraulic fluid tank serves to feed a hydraulic brake circuit. Specifically, the hydraulic brake circuit may comprise a master cylinder connected to braking apparatus including at least one wheel of the vehicle. In order to feed the hydraulic brake circuit, the hydraulic fluid tank feeds more particularly a primary chamber and a secondary chamber of said master cylinder. Feeding the primary and secondary chambers of the master cylinder enables primary and secondary pistons respectively to compress a volume of hydraulic fluid contained in said chambers and to move brake pads against at least one disk of a vehicle wheel hub. By compressing a volume of hydraulic fluid, at least one vehicle wheel is impeded and the vehicle can brake.
While the vehicle is in use, it is found that abnormal loss of hydraulic fluid occurs from inside the tank. Such loss of hydraulic fluid requires a vehicle driver to verify regularly that the level of hydraulic brake fluid inside the tank is sufficient. The level of hydraulic brake fluid is sufficient so long as there is enough hydraulic fluid inside the tank to ensure that the hydraulic brake circuit will operate. The level of hydraulic fluid therefore needs to be verified by a vehicle user by comparing the level of hydraulic fluid with a mark situated on a wall of the tank, for example. It is tedious that driver safety needs to be ensured by regularly verifying the level of hydraulic fluid in the tank, and adding fluid, when necessary. Regularly adding hydraulic fluid to the tank can also become expensive for the user of the vehicle.
Unfortunately, while the vehicle is in use, the volume of hydraulic fluid inside the tank can be caused to move. More particularly, the hydraulic fluid is caused to move suddenly in a direction of vehicle advance or in an opposite direction whenever the vehicle decelerates or accelerates suddenly. The hydraulic fluid can also move sideways relative to the travel direction of the vehicle, for example when the vehicle is making a turn. The tank may also take up a sloping position relative to the level of hydraulic fluid in the tank when the vehicle is running on a sloping road.
By moving inside the tank, the volume of hydraulic fluid can be caused to cover a tank feed orifice. The hydraulic fluid tank has an orifice for feeding it with hydraulic fluid that is closed by means of a stopper. This stopper covers the feed orifice and is usually screwed into place. When the fluid occupies the feed orifice, hydraulic fluid can escape from the tank by infiltrating between a thread on the feed orifice and a thread on the stopper. The fluid can also escape from the tank via an air vent made in the stopper. The air vent constitutes a small hole allowing air to enter into the tank. Air needs to be admitted in order to make it easier to feed the hydraulic circuit with hydraulic fluid.
In order to prevent fluid escaping from the tank, it is possible to increase the volume of the tank in a vertical direction relative to the vehicle travel direction so that the surface level of the volume of hydraulic fluid inside the tank practically never reaches the feed orifice of the tank while the vehicle is in use. However, increasing the volume of such a tank increases the space it occupies under a vehicle hood. In addition, increasing the volume of the tank does not completely prevent fluid from escaping from the tank.